1. Field of the Invention
The present invention relates to a discrimination card carried on person, for confirming the bearer by means of a secret code assigned to the bearer, which includes a memory for memorizing the erroneous input operation of the secret code and is constructed so as to render the card useless if erroneous inputs take place for a prescribed number of times in a row.
2. Description of the Prior Art
In a prior art discrimination card with built-in CPU and memory which is used for banking and other purposes, there is known a method of rendering the card useless by detecting the erroneous input operations for a prescribed number of times by a card reader/writer, in order to prevent illicit uses of the card. The method described above is disclosed in Japanese Patent No. 828847.
Furthermore, a method of permanently holding the traces of the erroneous input operations in the memory of the card to render the card useless on its own, when the cumulative frequency of erroneous inputs exceeds a prescribed number, is disclosed in Japanese Patent Publication for opposition No. 52-7649. However, in the above method, the card will become useless automatically when the cumulative frequency of erroneous inputs exceeds a prescribed number, even when the erroneous inputs took place due to careless operation, so that it has a defect in that it cannot discriminate whether an erroneous input was made carelessly or on purpose of illicit use.
To solve the above defect, there is disclosed in Japanese Patent Publication No. 57-29498 a card with a system by which the processing apparatus in the card detects the frequency of successive erroneous inputs by specially arranging for memorizing a successful operation subsequent to an erroneous input operation, to judge whether the number of successive erroneous inputs is less than a prescribed member.
However, the above system has a defect in that it requires a special memory for memorizing a successful operation subsequent to an erroneous input operation.